Medical Treatments

Medical management of urinary incontinence includes the use of drugs aimed at improving urethral tone via the alpha-1 adrenoceptors (α1-ARs). Phenylpropanolamine (PPA) is currently the drug that results in continence in the most dogs. Side effects in dogs include restlessness, anxiety, hypertension and tachycardia. This class of drugs is not recommended in patients with cardiac disease or hypertension.

Estrogens may also be used for urinary incontinence and these hormones are thought to sensitize the α1-AR to the norepinephrine and indirectly result in an improvement in the closure pressure. The lowest possible dose of estrogen should be used. Diethylstilbestrol (DES) is the most commonly prescribed form of estrogen for this disease. Bone marrow suppression has been described in dogs receiving older generation depot estrogens and in those receiving very high doses of DES. If the patient is still experiencing UI while receiving an α1-AR agonist, estrogen can be given concurrently.

Collagen Injections

Submucosal urethral collagen injections are now available for animals that are refractory to medications or for owners who do not wish to continually medicate their pet. Patients are placed under general anesthesia and three to four collagen deposits are injected in a circular fashion approximately 1.0 cm distal to the trigone via the cystoscope. The collagen acts as a bulking agent to create a 'mechanical' urethral obstruction and improve incontinence. Some dogs still require medications after this procedure, but greater continence is usually gained following the implants when drugs were previously ineffective. A second series of implants may be needed to improve continence in some dogs. Retreatment with collagen is usually easier and often successful in gaining continence in these dogs.